Java view technologies and frameworks: Difference between revisions

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{{Short description|Programming language and libraries}}

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'''Java view technologies and frameworks''' are [[web-based]] [[software libraries]] that provide the [[user interface]], or "[[Model–view–controller|view-layer]]", of [[Java (programming language)|Java]] [[web application]]s. Such [[application framework]]s are used for defining [[web page]]s and handling the [[HTTP]] [[List of HTTP header fields#Requests|requests]] (clicks) generated by those web pages. As a sub-category of [[web framework]]s, view-layer frameworks often overlap to varying degrees with web frameworks that provide other functionality for Java web applications.

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(This page is work-in-progress)

Java view-layer frameworks often claim to support some or all of the [[model–view–controller]] design pattern.

A plethora of Java Web Frameworks have mushroomed in the recent years. Some of them are in direct competition, which others are complimentary technologies. It is therefore necessary to understand where exactly each technology/framework fits into the J2EE scheme of things. This page lists the "View Technologies". These are the frameworks which are used for defining the web pages and the Server side programs which handle the requests (clicks) generated by the web pages.

==At a glance==

{| class="wikitable"

|-

! Action-based frameworks:

| [[Apache Struts]], [[Spring Framework|Spring MVC]]

|-

! Component-based frameworks:

| [[Apache Click]], [[Apache Tapestry]], [[Apache Wicket]], [[Jakarta Faces]]

|-

! Web template systems:

| [[Apache Tiles]], SiteMesh, [[Thymeleaf]]

|-

|}

* [[Jakarta Faces]] (JSF), [[Apache Tapestry]] and [[Apache Wicket]] are competing component-based technologies, abstracting the [[Stateless protocol|stateless]] HTTP request-response cycle and the [[Jakarta Servlet]] [[API]] behind an [[Object-oriented programming|object-oriented]], event-driven component model.

* In contrast, Struts and the [[Spring Framework|Spring MVC Framework]] are action-oriented frameworks that provide a thinner [[abstraction layer]] over the servlet [[API]].

* Apache Tiles is a templating framework designed to work with Struts.

* [[Facelets]] is a view definition and templating technology designed to work with JSF.

* SiteMesh can be used with any [[Jakarta Server Pages|Jakarta Pages]] (JSP).

* Facelets, Tapestry and Wicket have their own templating approaches based on [[HTML]]/[[XHTML]].

* [[Apache Click]] uses HTML based [[Apache Velocity]] templates and [[plain old Java object]]s (POJOs), with JSP optional.

==Servlet API==

{{main |Jakarta Servlet}}

This is the foundation of almost all Java View technologies. It provides the basic framework for writing Java classes, called 'Servlets' that can respond to HTTP Requests, create Cookies and maintain Sessions.

The Servlet API is the foundation of almost all Java Web View technologies. Servlet provides the basic mechanism for writing Java [[class (computer programming)|class]]es for web applications. Servlets can respond to HTTP requests, create cookies and maintain sessions.

==Jakarta Pages (JSP) ==

{{main |Jakarta Server Pages}}

* Built on top of the Servlet API, JSP provides a document-centric, tag-based templates, server programming model which can generate many forms of textual content.

* Java code may be embedded in JSP files and is compiled and executed when a request is received.

==Apache Struts==

{{main |Apache Struts}}

* Struts provides for a [[coupling (computer programming)|decoupling]] of the Controller and the View.

* Requests are received by a Java Class (Controller) which can decide which View to display.

* The actual View can be written in different view technologies, like JSP, free marker template, velocity template etc.

* An XML [[configuration file]] is used to specify the "Page Navigation", i.e. the flow of the request to the appropriate Controller, and which View to display based on the outcome of the Controller.

* '''Competitor''': Spring MVC, Grails

==Apache Tapestry==

{{main |Apache Tapestry}}

* A component-based view framework.

* Classes are written as POJOs and byte-code transformed at runtime

* Configured with annotations and naming conventions rather than XML

* Compared to JSPs, enforces a clear separation of [[HTML element|HTML markup]] and Java code.

* HTML templates can be directly previewed by web designers

* Changed component classes are live-reloaded into running application for faster development.

* Uses the [[Post/Redirect/Get]] navigation pattern for form submission.

* '''Competitor''': Wicket, JSF

==Apache Tiles==

{{see also |d:Special:EntityPage/Q28912908|l1=Apache Tiles}}

* This is an HTML templating framework based on the [[composite pattern]].

* It allows for the HTML page to be broken up into multiple "pagelets", called Templates, Definitions and Composing pages.

* At [[runtime (program lifecycle phase)|runtime]] the pagelets are stitched together to generate the final HTML. Pages are written in JSP.

* '''Competitor''': SiteMesh

==Apache Wicket==

{{main |Apache Wicket}}

* A component-based view framework.

==JSP==

* Pages directly interact with stateful Java components on the server.

Built on top of the Servlet API, JSP provides for a HTML centric Server programming model. Java code is embedded in the JSP files and is executed when a request is received.

* Components and their state are managed by the Wicket framework, freeing the application developer from having to use HttpSession directly to manage state.

* Does not require XML for configuration.

* Compared to JSPs, enforces a clear separation of [[HTML element|HTML markup]] and Java code.

* Web page components are 'pushed' into the HTML markup from the code.

* '''Competitor''': Tapestry, JSF

==Jakarta Faces and Facelets==

==Struts==

{{main |Jakarta Faces}}

Built on top of the Servlet API, Struts provides for decoupling between the Controller and the View. Requests are received by a Java Class (Controller) which can decide which View to display. An XML configuration file is used to specify the "Page Navigation", i.e. the flow of the request to the appropriate Controller, and which View to display based on the outcome of the Controller. The actual View is written as a JSP page.

* A specification for component-based view frameworks.

'''Competitor''': Though Struts does not have any direct competitor in its league, Component View Technologies (like Wicket, Tapestry) are generally accepted as superior.

* [[Eclipse Mojarra]] and [[Apache MyFaces]] implementations are available

* Typically uses Facelets for XML/XHTML-based templating.

* Classes are written as POJOs, with Annotations or XML configuration files used to associate them with page and component templates.

* The [[Unified Expression Language]] allows binding component fields and events to POJO bean properties and methods.

* Conversion and validation constraints can be specified in Facelets and are automatically applied, normally resulting in reposting of the same page with error information in case of failure.

* Navigation can be via configuration file rules or directly specified in the page.

* Can transparently support [[Ajax (programming)|Ajax]].

* '''Competitor''': Wicket, Tapestry

==TilesSiteMesh==

{{main |SiteMesh}}

This is a HTML templating framework based on the "Composite" model. It allows for the HTML page to be broken up into multiple pagelets, called Templates, Definitions and Composing pages. At run time the pagelets are stitched together to generate the final HTML. Pages are written in JSP.

* SiteMesh is an HTML templating framework based on the "Decoration" model.

'''Competitor''': Sitemesh

* It allows for the creation of a 'decoration' template which is then applied to any other HTML to generate a new HTML.

* The newly generated HTML contains elements from the original HTML blended into the template.

* This allows for the original HTML to be very simple and devoid of any formatting or layout specification. The template, in turn, is devoid of any actual information.

* Blending the two allows for a consistent [[look and feel]] for all [[web page]]s.

* '''Competitor''': Tiles

==SitemeshSpark==

{{main |Spark (software)}}

This is a HTML templating framework based on the "Decoration" model. It allows for the creation of a 'decoration' template which is then applied to any other HTML to generate a new HTML. The newly generated HTML contains elements from the original template blended into the template. This allows for the original HTML to be very simple and devoid of any formatting or layout specification. The template, in turn, is devoid of any actual information. Blending the two allows for a consistent look and feel for all web pages.

* Spark a micro web framework built around a simple routing system

'''Competitor''': Tiles

* It runs on an embedded [[Jetty (web server)|Jetty]] web server by default, but can be configured to run on other webservers.

* It supports three different templates engines: [[Apache Velocity|Velocity]], [[FreeMarker]] and [[Mustache (template system)|Mustache]]

* It aims to facilitate rapid development, and does not make use of annotations or proprietary solutions.

==WicketSee also==

{{Portal|Computer programming}}

Provides a 'Component' view technology - meaning the Request-Response Stateless paradigm of HTTP is abstracted away to give rise to a Object Oriented Stateful paradigm. Pages now directly interact with Stateful Java Components on the server. Components and their State are managed by the Wicket framework, freeing the application developer from having to use HttpSession directly to manage state themselves. Further, Wicket provides for a clear separation of HTML markup from code, and there are no XML configuration files to manage.

* [[List of web service frameworks]]

* [[List of Java frameworks]]

[[Category:Java (programming language)]]

'''Competitor''': Tapestry, JSF

[[Category:Java APIs]]